The Mechanical Properties Of Sands Mixed With Carbonate Soils

The carbonate mixed sand,as a special rock and soil material,is mainly distributed in tropical coastal areas.Because of the influence of its sedimentary environment,the carbonate mixed sand is of special origin and fabric,thus affecting its physical and mechanical properties.The results show that the content of calcium carbonate is the main factor affecting the mechanical properties of carbonate sand and quartz sand,and a great deal of research results have been made at home and abroad on the mechanical properties of carbonate sand and quartz sand.However,the study on the mechanical properties of carbonate mixed sand is not sufficient.The study of the geotechnical characteristics of the carbonate mixed sand is not only beneficial to the inclusion of carbonate rock and soil materials into the current classification system of rock and soil,and to perfect the theory and technology of geotechnical mechanics.At the same time,further implementation will also direct service to our country's marine strategy and the Belt and Road initiative.In this paper,the mixed sand prepared by different mass percentages of coral sand and terrestrial quartz sand in the South China Sea is studied by means of chemical,physical and mechanical combination,and the microscopic and macroscopic research methods are used to reveal the fine morphology of the coral sand particles and the strength and change of the mixed sand with the content of calcium carbonate.The influence of shape characteristics.The main contents and conclusions are as follows:1.The carbonate mixed sand from Sanya beach was measured by EDTA volumetric titration,elemental analysis,atomic absorption spectrometry and X-ray diffraction,respectively,and the content of calcium carbonate was measured by atomic absorption spectrometry(AAS)and X-ray diffraction(XRD).The advantages,disadvantages and accuracy of the five methods are analyzed and compared,and the EDTA volumetric titration method was selected to be the most suitable for mixing.2.Using optical microscope to take photos of coral sand and quartz sand particles and use Image-pro Plus software to deal with the analysis of particle photos.Five particle shape parameters such as global profile coefficient,sphericity,edge angle,roughness and flatness of different grain groups of coral sand and quartz sand were calculated.The difference of particle shape between two kinds of sand particles and different particle size groups was analyzed and compared.The main parameters of the sand particle shape parameters are the edge angle Ag.3.The typical particle size grading was selected to carry out the three axis consolidation drainage test of mixed sand,and the influence of carbonate content on the strength and deformation of mixed sand was revealed.The study shows that the stress-strain curve of the mixed sand is strain softening.With the increase of calcium carbonate content,the peak strength of the stress-strain curve increases.In the low stress state,the content of calcium carbonate has little effect on the body change,and the mixed sand with low calcium carbonate content under high stress state is first shear dilation,and the mixed sand body with high calcium carbonate content under high stress shows a complete shear shrinkage.4.The C value of shear strength parameters of mixed sand with different calcium carbonate content showed an approximately linear growth trend with the increase of calcium carbonate content.The internal friction angle value showed an approximate linear slow growth with the increase of calcium carbonate content,and the change range was not large.Increase the initial shear modulus of different calcium carbonate content of sand mixed with the confining pressure increases,the major effect of calcium carbonate content of the initial shear modulus is low in calcium carbonate content should stress increase the effect of the initial shear modulus in high stress state is first increased and then decreased.5.The crushing rate of Br with carbonate mixed sand increases with the increase of effective confining pressure.Under the same conditions,the relative crushing rate Br increases with the increase of calcium carbonate content.